This invention relates generally to rock drills and more particularly to pneumatically operated percussive drills of the type adapted to be inserted into the drillhole being drilled. Such a drill is commonly known as a "down-the-hole" drill (DHD).
Many applications for down-the-hole drills require that liquids such as water, and other matter, be injected into the drill air supply to provide improved hole cleaning and stabilization. Typically, the volume of liquids injected can range from about 2.0 gallons per minute to about 15.0 gallons per minute. When water is injected into the air flow for a DHD, an appreciable loss in penetration rate results for a given pressure. One approach to avoiding this penetration rate loss is to separate the water, and other matter, from the percussive fluid in the drill string at or near the drill itself, before the percussive fluid actuates the drill piston. This separated water and other matter can then be exhausted into the drillhole to effect debris removal.
One such device for accomplishing this separation is disclosed in a pending U.S. patent application, Ser. No. 07/766,866, filed Nov. 29, 1991, entitled "A DEVICE FOR REMOVING DEBRIS FROM A DRILLHOLE" of which I am a co-inventor. This device positions a separator outside the DHD proper, adjacent the backhead of the drill. It would be useful if there were such separator device that is adapted to fit within existing drill backheads, so that the separator can be simply added to the drill backheads, as an add-on unit or as part of the complete drill, for newly manufactured units.
The foregoing illustrates limitations known to exist in present down-the-hole drilling technology. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.